Lead frames as chip carriers are widely implemented in semiconductor packages. Normally, the lead frame is completely made of metal having a plurality of metal leads and a baffle paddle where the metal leads are for electrical connections of the chip and the baffle paddle is configured to change the mold flows of molding compounds and further to balance the top and bottom mold flow to manufacture good quality encapsulant for encapsulating the chip. In a conventional lead frame-based semiconductor package, Lead-On-Chip, LOC, the leads can replace die pads for die attachment. However, in order to balance the top and bottom mold flow during encapsulation, the baffle paddle is adjusted to be “downset” in a different plane as the leads whether using chip carriers with die pads or LOC leads. Therefore, the connections of the baffle paddle have to be bent causing shifting and twisting of the corresponding connected leads leading to inaccurate die attachment and wire-bonding difficulties.
As shown in FIG. 1, a conventional lead frame 100 primarily comprises a plurality of leads 110, at least a baffle paddle 120, and a plurality of internal tie bars 130. The leads 110 are disposed at two opposing longer sides of the lead frame 100 and the baffle paddles 120 are disposed at two opposing shorter sides of the lead frame 100. The baffle paddies 120 are connected to a dam frame 140 of the lead frame 100 by a plurality of external tie bars 121 and is also connected to an adjacent one 111 of the lead 110 by the internal tie bar 130 to prevent the baffle paddle 120 from shifting during molding. The internal tie bar 130 is completely encapsulated in a semiconductor package, but the external tie bars 121 have one ends exposed from the semiconductor package. Before semiconductor packaging processes, the leads 110, 111, and the baffle paddle 120 are integrally connected and firmly held to the dam frame 140. As shown in FIG. 2 and FIG. 3, when a downset is formed on the internal tie bar 130 and the external tie bars 121 to make the baffle paddle 120 downset with respect to the leads 110, a downset bend 131 having creases is formed between the internal tie bar 130 and the baffle paddle 120 so that the leads 110 are formed on the first plane 101 and the baffle paddle 120 on the second plane 102 in parallel, respectively. As shown in FIG. 2, the internal tie bar 130 experiences a force pulling downward to create a shifting displacement D1 and to twist the connected lead 111 to create a twisting displacement D2 when forming the downset bend 131. A die-attaching tape 150 is attached to the bottom surfaces of the leads 110 including the lead 111 for attaching a chip, not shown in the figure. As shown in FIG. 2 and FIG. 3, since the lead 111 is pulled and twisted with the twisting displacement D2 so that lead 111 can not be in the same plane as the rest of the leads 110, therefore, the die-attaching tape 150 can not completely attach to the active surface of a chip. Therefore, the die-attaching tape 150 can not closely attach to the chip during die-attaching processes, the bonding strengths between the chip and the leads 110, 111 are reduced leading to easily peeling of the chip. Moreover, the twisting displacement D2 of the lead 111 will cause the wire-bonding surface of the lead 111 to be twisted and shifted leading to difficulties in wire bonding.